On the Dynamic Detonation Parameters in Acetylene-Oxygen Mixtures with Varying Amount of Argon Dilution

Zhang, B.; Mehrjoo, Navid; Ng, Hoi Dick; Lee, J. H. S.

doi:10.1007/978-3-319-16835-7_42

Cited by 6 publications

(5 citation statements)

References 19 publications

(25 reference statements)

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“…A high‐voltage electric spark was used to supply powerful initiation energy in our previous direct detonation initiation research . In this study, the spark energy (1/2 CV 2 ) generated by a slender coaxial electrode is 40 J, which is used to initiate all the mixtures and establish an identical ignition condition for all methane–air mixtures.…”

Section: Methodsmentioning

confidence: 99%

Explosion and flame characteristics of methane/air mixtures in a large‐scale vessel

Zhang

Chen

Xiu

et al. 2014

Process Safety Progress

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In this study, experiments of explosions and flame characteristics in methane/air mixtures are performed in a 10-m 3 vessel. Pressure gauges and a high-speed camera are utilized to record the pressure trajectories and the flame propagation process of ignition growth. The experimental results show that the maximum value of overpressure and the maximum rate of the explosion pressure rise are 0.596 MPa and 1.82 MPa/s for the methane (9.5% in volume)/air mixture at atmospheric conditions, respectively. Both values are higher than for other mixtures with different compositions. The results also indicate that the overpressure from the large-scale vessel in this study is lower than that of a smaller apparatus (e.g., 5-L closed cylindrical vessel). This difference occurs due to the cooling effect and because the reflected sonic disturbances by the vessel wall affect the explosion process and weaken the energy during the pressure attenuation stage, thus rendering the value of overpressure in the large-scale apparatus lower than in the tiny cylindrical vessels. The maximum overpressure is observed at 0.75 m for C 5 7% ("C" means the methane concentration) and 9.5% but at 1.3 m for C 5 5%, 6.5%, 11.2%, and 13%. These results indicate that methane/air is an easier means to generate overpressure and that the overpressure is higher near the stoichiometric condition. Based on the analysis of the flame propagation process, the mean value of the flame speed of methane (C 5 9.5%)/air is calculated to be approximately 2.43 m/s because the nonuniformity of the chemical reaction at the flame front results in a maximum fluctuation of flame speed of approximately 28.5%. The flame thickness (u) of methane (C 5 9.5%)/air fluctuates between 9.84 and 10.95 mm, with a mean value of 10.53 mm.

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Section: Methodsmentioning

confidence: 99%

Explosion and flame characteristics of methane/air mixtures in a large‐scale vessel

Zhang

Chen

Xiu

et al. 2014

Process Safety Progress

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“…Hence, it is crucial to understand the oblique detonation structures with inflow perturbations [27][28][29]. In normal detonations, the initiation features and their correlation with other dynamic parameters such as cell width have been studied widely [30][31][32][33], but only few equivalent studies are performed on the ODW formation especially including inflow disturbance such as non-uniformity in the mixture equivalence ratio denoted in this paper by "ER". Sislian et al [34] described the effects of incomplete fuel/air mixing on two types of ramjets performance characteristics by assuming a Gaussian distribution of equivalence ratio in the combustible mixture flow, and the deflagration distortion is observed clearly.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of inflow equivalence ratio inhomogeneity on oblique detonation formation in hydrogen–air mixtures

Fang

Teng

et al. 2017

Aerospace Science and Technology

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In this study, numerical simulations using Euler equations with detailed chemistry are performed to investigate the effect of fuel-air composition inhomogeneity on the oblique detonation wave (ODW) initiation in hydrogen-air mixtures. This study aims for a better understanding of oblique detonation wave engine performance under practical operating conditions, among those is the inhomogeneous mixing of fuel and air giving rise to a variation of the equivalence ratio (ER) in the incoming combustible flow. This work focuses primarily on how a variable equivalence ratio in the inflow mixture affects both the formation and characteristic parameters of the oblique detonation wave. In this regard, the present simulation imposes initially a lateral linear distribution of the mixture equivalence ratio within the initiation region. The variation is either from fuel-lean or fuel-rich to the uniform stoichiometric mixture condition above the oblique shock wave. The obtained numerical results illustrate that the reaction surface is distorted in the cases of low mixture equivalence ratio. The so-called "V-shaped" flame is observed but differed from previous results that it is not coupled with any compression or shock wave. Analyzing the temperature and species density evolution also shows that the fuel-lean and fuel-rich inhomogeneity have different effects on the combustion features in the initiation region behind the oblique shock wave. Two characteristic quantities, namely the initiation length and the ODW surface position, are defined to describe quantitatively the effects of mixture equivalence ratio inhomogeneity. The results show that the initiation length is mainly determined by the mixture equivalence ratio in the initiation region. Additional computations are performed by reversing ER distribution, i.e., with the linear variation above the initiation region of uniform stoichiometric condition and results also demonstrate that the ODW position is effectively determined by the ER variation before the ODW, which has in turn only negligible effect on the initiation length.

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“…Detonation waves are supersonic combustion waves that can sustain themselves in a premixed combustible mixture (Zhang, Ng & Lee 2012; Zhang et al. 2014; Shi, Uy & Wen 2020). Due to their self-ignition, fast energy release and high thermal cycle efficiency, detonation phenomena as a combustion mode have attracted increasing attention in the development of hypersonic propulsion systems (Kailasanath 2000; Wolański 2013; Lu & Braun 2014).…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of the destabilized Mach reflection of inviscid oblique detonation waves before an expansion corner

2022

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The stabilization of oblique detonation waves (ODWs) in an engine combustor is important for the successful applications of oblique detonation engines, and comprehensively understanding the effects of the inviscid reflection of ODWs on their stabilization and the relevant mechanisms is imperative to overall combustor design. In this study, the flow fields of ODW reflections in a space-confined combustor are numerically studied by solving the two-dimensional time-dependent multispecies Euler equations in combination with a detailed hydrogen combustion mechanism. The inviscid Mach reflections of ODWs before an expansion corner are emphasized with different flight Mach numbers, Ma, and different dimensionless reflection locations, ζ ≥ 0 (ζ = 0: the ODW reflects precisely at the expansion corner; ζ > 0: the ODW reflects off the wall before the expansion corner). Two kinds of destabilization phenomena of the inviscid Mach reflection of an ODW induced by different mechanisms are found, namely wave-induced destabilization at large ζ > 0 for moderate (not very low) Ma and inherent destabilization at any ζ > 0 for low Ma. Wave-induced destabilization is attributed to the incompatibility between the pressure ratio across the Mach stem and its relative propagation speed, which is triggered by the action of the secondary reflected shock wave or the transmitted Mach stem on the subsonic zone behind the Mach stem. Inherent destabilization is demonstrated through an in-depth theoretical analysis and is attributed to geometric choking of the flow behind the Mach stem.

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On the Dynamic Detonation Parameters in Acetylene-Oxygen Mixtures with Varying Amount of Argon Dilution

Cited by 6 publications

References 19 publications

Explosion and flame characteristics of methane/air mixtures in a large‐scale vessel

Explosion and flame characteristics of methane/air mixtures in a large‐scale vessel

Numerical study of inflow equivalence ratio inhomogeneity on oblique detonation formation in hydrogen–air mixtures

Mechanisms of the destabilized Mach reflection of inviscid oblique detonation waves before an expansion corner

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